Kirazli et al.: The relationship between parental defense intensity and nest site characteristics in Eurasian magpie - 1293 - THE RELATIONSHIP BETWEEN PARENTAL DEFENSE INTENSITY AND NEST SITE CHARACTERISTICS IN EURASIAN MAGPIE (PICA PICA L.) - AN ASSESSMENT WITH THE CLASSIFICATION METHODS KIRAZLI, C.1* – KAN KILINÇ, B.2 – YAMAÇ, E.3 1Abant İzzet Baysal University, Faculty of Agriculture and Natural Sciences, Department of Wildlife Ecology and Management, 14280 Bolu, Turkey 2Anadolu University, Science Faculty, Department of Statistics, 26470 Eskişehir, Turkey e-mail: [email protected] 3Anadolu University, Science Faculty, Biology Department, 26470 Eskişehir, Turkey e-mail: [email protected] *Corresponding author e-mail: [email protected] (Received 16th Jan 2017; accepted 20th Mar 2017) Abstract. Nest defense behavior varies among species and depends on different factors. However little is known of the influence of urbanization and nest characteristics on the nest defense intensity as parental investment of the bird species. We observe the Eurasian magpie Pica pica nests to evaluate their nest defense behavior among those factors including urbanization degree of habitat, and nest characteristics such as nest volume, presence/absence of roof, offspring size and the number of offspring reduction for each breeding stages (incubation, early brooding and post brooding stage). To investigate the relationship between the nest defense behavior of Eurasian magpie and a set of those factors we used classification trees, binary logistic regression and random forest. According to our results nest defense strategies can be temporally changed primarily according to the nest volume with the auxiliary agents mostly a reduction of offspring number, which indicates parental capacities and offspring conditions could shape strongly their own nest defense strategies. Besides, we recommend classification trees, binary logistic regression and random forest modeling approaches to be considered individually or together for predictive mapping for ecosystem scientists. Keywords: nest defense, urbanization, offspring conditions, nest volume, binary logistic regression Introduction Parental investment in offspring which have been shaped by natural selection is a tradeoff factor between reproduction output and parents budget of energy and time. Although parents can enhance the investment in offspring by increasing the intensity of nest defense over the breeding period (Redondo, 1989; Caro, 2005), nest defense behavior may vary among species and depending on offspring age (Curio et al., 1985; Montgomerie and Wheatherhead, 1988; Redondo, 1989), probability of parents’ survival/renesting (Pavel and Bureš, 2008; Tilgar and Kikas, 2009), clutch/brood size (Olendorf and Robinson, 2000; Tilgar and Kikas, 2009; Svagelj et al., 2011), vulnerability level of offspring to predation (Redondo, 1989; Brunton, 1990), age linking residual reproductive value (Takata et al., 2016) and conditions of broods (Pavel and Bureš, 2001). APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 15(3): 1293-1308. http://www.aloki.hu ● ISSN 1589 1623 (Print) ● ISSN 1785 0037 (Online) DOI: http://dx.doi.org/10.15666/aeer/1503_12931308 2017, ALÖKI Kft., Budapest, Hungary Kirazli et al.: The relationship between parental defense intensity and nest site characteristics in Eurasian magpie - 1294 - Besides, the nest defense behavior which is the crucial thing of the parental investment is affected by the parents’ quality (Hogstad, 2005). As it is commonly thought that successful parents as ‘good’ male and female (in terms of quality) should provide better nest conditions. So ‘good’ nest conditions should represent parental quality. In magpies, the roof structure of nests and nest volume are good indicators of parental quality as reflected parents’ willingness to invest more in offspring (Soler et al., 1998; De Neve and Soler, 2002; De Neve et al., 2004; Quesada, 2007). Also, Møller (1990) indicated that nest volume probably covaries with the nest site quality and parents' nest defense intensity. In addition, high-quality habitat is accepted for minimizing the cost of reproduction effort of parents, and maximizing the survival chance of parents and fledging success (Hogstedt, 1981; Klopfer and Ganzhorn, 1985). Accordingly, it may refer to a direct relationship between those factors including parental quality, nest characteristics and nest site choice of parents. Thus, selection of high-quality habitat can be an indicator of parental investment. Recent studies indicated that some generalist bird species called as urban adapters are able to maintain their reproduction output and reproductive success, and can benefit from the urbanized areas according to their tolerance to the urban stresses such as roads, build-up areas and disturbing conditions associated with human activities (Sawmiller, 2012; Yamaç and Kirazlı, 2012; Morelli et al., 2014). So ability to take advantage of urbanization can influence the ecological and life history traits of flexible generalist species (François et al., 2008; Balasubramaniam, 2014). For example magpies Pica pica as an urban adapter species have changed nest characteristics and added new food source, and thus they are successfully colonized in urban environments (Jerzak, 2001; François et al., 2008; Krystofkova et al., 2011; Kang et al., 2012). Because of less predator pressure and more accessible anthropogenic food resources, species spend their time and energy to rear successfull fledglings in the breeding period (Soler et al., 1995; Jerzak, 2001; François et al., 2008; Yamaç and Kirazlı, 2012). So it can be expected that magpies change their nest defense strategies in urban area which is the high-quality habitat for species. If such nest characteristics (nest volume, roof) and nest site choice are good indicators of the parental quality and ‘good’ quality of nest and nest site provide reproductive success, the amount of investment in offspring and nest defense intensity of parents should vary according to nest site choice and nest characteristics. In this regard we predicted that in magpies species-specific nest defense behavior could be change during the breeding period according to the nest volume and presence/absence of roof (roofed or unroofed nest), and the gradient of urbanization (urban or rural habitat). Previous studies in magpies revealed that nest defense behavior has a link with offspring age but not offspring size. Because of broods future reproductive probabilities increasing with offspring age correlates positively with lifetime reproductive success of parents (Redondo and Carranza, 1989). Nest defense increases with an increase of offspring number closing to the optimal size, however (Montgomerie and Weatherhead, 1988; Caro, 2005). Offspring size (number of offspring) certainly depends on the reproductive potential of the parents and also the potential differences of parents can generate different optimum size of offspring. Even so, it is argued that offspring size has minimal effects to the life histories of parents. Besides, parents can evaluate the amount of investment according to the number of offspring reduction rather than offspring size during the breeding period (De Steven, 1980; Tolonen and Korpimӓki, APPLIED ECOLOGY AND ENVIRONMENTAL RESEARCH 15(3): 1293-1308. http://www.aloki.hu ● ISSN 1589 1623 (Print) ● ISSN 1785 0037 (Online) DOI: http://dx.doi.org/10.15666/aeer/1503_12931308 2017, ALÖKI Kft., Budapest, Hungary Kirazli et al.: The relationship between parental defense intensity and nest site characteristics in Eurasian magpie - 1295 - 1995; Tilgar and Kikas, 2009). Thus, a considerable contribution of the number of offspring reduction might be found on the nest defense strategies of magpie parents rather than offspring size. Due to ecological and behavioral flexibility, Eurasian magpie Pica pica is urban adapted species in the Palearctic Region (Jerzak, 2001). On the other hand knowledge about the effect of urbanization as a high-quality habitat on the nest defense intensity is insufficient. The main objective in the present study is to evaluate the role of nest site with the other crucial effects such as nest characteristics, clutch/brood size and the number of clutch/brood reduction on nest defense intensities of the urban-adapting magpies, and to classify the influence level of those predictor variables. Material and methods Study site Our study was conducted at two nest sites, close to two different road types in Eskisehir (39o47′ N, 30o31′ E), northwest Turkey. The first road is a multi-lane highway and provides transportation between the cities of Eskişehir and Bursa. The traffic flow is quite heavy with cars and trucks all year round. The traffic density was estimated at 17302 vehicles/24 h in 2009 (General Directorate of Highways, 2010). The second nest site is located near a dirt road constructed from the natural material of the land surface (General Directorate of Highways, 2010). This road provides transportation to an agricultural area and to Karagözler village, and is generally used by farmers and villagers. The traffic density was approximately 100 vehicles /24 h in 2009 (General Directorate of Highways, 2010). According to our comparative analysis of comparison, both nest sites had similar habitat conditions except for road type (Yamaç and Kirazlı, 2012), and included open agricultural fields. The greatest number of nest trees in both area was usually between the road and agricultural fields. The Black